Direct Monte Carlo Simulations of Air Bearing Characteristics on Patterned Media

In patterned media recordings such as discrete track and bit-patterned media (BPM) recordings, the presence of pattern structures on the media surface causes the slider air bearing problems more complicated to be analyzed and studied. Using the 3-D direct simulation Monte Carlo (DSMC) method, the plain slider surface and bit/discrete track-patterned disk surface are designed for case studies in this paper. This paper reports the local bearing pressure variations acted on the slider surface due to the air bearing effects of pattern structures on the disk surface using the DSMC method. From the results obtained under the steady-state condition, it is observed that the bearing pressure profiles will be smoother and the bearing forces will approach to a stable value when the pattern pitch values are smaller than 0.4 μm. This critical pitch value is close to 0.3 μm that we reported previously based on modified Reynolds equations. We also investigate the effects of the pattern depth and total recess area ratio on the air bearing characteristics in BPM recording. Furthermore, in order to understand the effect of bit-pattern movements, we simulate the motion of bit-pattern structures by using four typical moving bit-pattern layouts. As of the outcomes, we can conclude that this effect could be negligible if the bit size is in several tens of nanometer scale.